1. Field of the Invention
The present invention relates to a driving circuit and a light emitting diode (LED) driving controller, and more particularly to the LED driving circuit and the driving controller having a function of latch protection.
2. Description of Related Art
Reference is made to FIG. 1 showing a schematic diagram of the conventional driving circuit. The driving circuit has a converting circuit including an inductor L, a diode D, a transistor switch SW, and a capacitor C, and a controller 10. The driving circuit is used to drive a load 30, and a resistor R couples to this load 30 which generates a feedback signal FB according to the current flowing through the load 30. The controller 10 then generates a control signal Gate to control on or off state of the transistor switch SW according to the feedback signal FB. Accordingly, an electric power transferred from an inputted voltage VIN to an output end of the converting circuit is modulated to stabilize the current flowing through the load 30.
The controller 10 includes an error amplification circuit 12, an oscillation circuit 14, a pulse width modulation circuit 16, a driving control circuit 18, and a protection circuit 20. The error amplification circuit 12 receives a reference voltage Vref and the feedback signal FB, and accordingly generates an error amplification signal COMP. The pulse width modulation circuit 16 receives the error amplification signal COMP and a ramp signal SAW outputted from the oscillation circuit 14, in order to generate a pulse width modulation signal PWM. The driving control circuit 18 generates the control signal Gate to control the transistor switch SW according to this pulse width modulation signal PWM. The protection circuit 20 outputs a protection signal PROT to the driving control circuit 18 when the driving circuit operates abnormally. Thus, the driving control circuit 18 may temporarily stop outputting the control signal Gate to stop the transfer of the inputted voltage VIN to the converting circuit. When the abnormally condition is removed, the protection circuit 20 stops outputting the protection signal PROT, and thus the driving control circuit 18 could re-transmit the control signal Gate to switch the on/off state of the transistor switch SW.
However, the root cause of abnormality may not be identified and eliminated by the stoppage of the transmission of the control signal Gate. The driving circuit may still operate abnormally again when the control signal Gate is re-transmitted to control the on/off state of the transistor switch SW. Therefore, the conventional approach may cause more power consumption, and more un-stable, and even increase the likelihood of damaging it.